It is a common practice in manufacturing operations involving indefinite length web materials to longitudinally transport the web in a desired path of travel for processing and/or collection. Typically in textile manufacturing operations, textile fabrics in indefinite length form are longitudinally moved in a path of travel for treatment, inspection, and/or collection in roll form. In such web handling operations, it is generally desirable and often essential that the web be precisely positioned during its longitudinal movement to ensure proper processing and roll formation during collection.
Various mechanical devices have been employed to engage the surface of a web and spread it to full width during its longitudinal movement, and other mechanical devices have been used to selectively engage and adjust the lateral position of a web during its movement in response to edge-sensing means. Bowed support rolls are commonly employed to laterally spread a web during its longitudinal movement, and mechanical guide elements located adjacent side edges of the path of travel of the web are employed to selectively engage the web in response to web edge-sensing means to laterally displace and ensure accurate location of the same during its longitudinal movement. One apparatus for controlling the lateral position of a moving web is disclosed in Young et al U.S. Pat. No. 4,068,789 and comprises a scroll roll having a pair of pressure applicators located adjacent side portions of the roll which are selectively movable into contact with the web in response to edge-sensing means to press the web against the scroll roll surface and cause lateral displacement of the web along the roll in desired direction. The patent discloses in one embodiment that a pressurized stream of air may be directed against the surface of the web to press it more firmly against the scroll roll such that the roll moves the web laterally to the right or left in response to edge sensing means.
It is also known to employ pressurized air to convey and/or smooth selected portions of a moving web of material during a web processing or web collection operation. The following U.S. Pat. Nos. disclose various apparatus utilizing pneumatic pressure for such purpose: 2,790,638 2,848,820 2,883,475 2,989,265 3,075,679 3,142,879 3,192,845 3,231,165 3,272,415 3,290,795 3,431,602 3,650,043 3,719,315
In the handling and processing of fragile or lightweight web constructions, such as flimsy, lightweight gauze fabrics and non-woven materials, it is difficult to accurately control the position of such webs in running length form by use of conventional mechanical spreading and guiding equipment which contact the web surface. Often the mechanical guide elements contacting the web will tear, snag, distort, or otherwise damage the web, and often are ineffective for properly positioning the web for processing or collection.